Compositions and methods for dry electrode films having reduced binder content

ABSTRACT

Materials and methods for preparing dry cathode electrode film including reduced binder content are described. The cathode electrode film may be a self-supporting film including a single binder. The binder loading may be 3 weight % or less. In a first aspect, a method for preparing a dry free standing electrode film for an energy storage device is provided, comprising nondestructively mixing a cathode active material, a porous carbon, and optionally a conductive carbon to form an active material mixture, adding a single fibrillizable binder to the active material mixture, nondestructively mixing to form an electrode film mixture, and calendering the electrode film mixture to form a free standing electrode film.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference under 37 CFR 1.57, andRules 4.18 and 20.6. This application claims the benefit as acontinuation of U.S. Non-Provisional patent application Ser. No.17/043,598, filed Sep. 29, 2020, which claims the benefit of priority toPCT Application Number PCT/US2019/032045, filed May 13, 2019, whichclaims the benefit of priority to U.S. provisional Patent ApplicationNo. 62/671,012, filed May 14, 2018 and titled “COMPOSITIONS AND METHODSFOR DRY CATHODE FILMS HAVING REDUCED BINDER CONTENT”, which areincorporated by reference herein in their entirety for all purposes.

BACKGROUND Field of the Invention

The present invention relates generally to energy storage devices, andspecifically to materials and methods for cathode electrode films havingreduced binder content.

Description of the Related Art

Electrical energy storage cells are widely used to provide power toelectronic, electromechanical, electrochemical, and other usefuldevices. Such cells include batteries such as primary chemical cells andsecondary (rechargeable) cells, fuel cells, and various species ofcapacitors, including ultracapacitors. Increasing the energy storagecapacity of energy storage devices, including capacitors and batteries,would be desirable for enhancing utility of energy storage in real-worlduse cases.

SUMMARY

For purposes of summarizing the invention and the advantages achievedover the prior art, certain objects and advantages of the invention aredescribed herein. Not all such objects or advantages may be achieved inany particular embodiment of the invention. Thus, for example, thoseskilled in the art will recognize that the invention may be embodied orcarried out in a manner that achieves or optimizes one advantage orgroup of advantages as taught herein without necessarily achieving otherobjects or advantages as may be taught or suggested herein.

In some embodiments, a dry cathode electrode film is provided. The drycathode film may advantageously be a free standing electrode filmcomprising a battery cathode active material, and having less than about3% binder loading of a single fibrillizable binder.

In a first aspect, a method of fabricating a dry electrode film of anenergy storage device is disclosed. The method includes mixing an activematerial with a porous carbon material to form a dry active materialmixture, mixing the dry active material mixture with a dry binder toform a dry electrode film mixture, and calendering the dry electrodefilm mixture to form a free-standing dry electrode film with a binderloading of at most about 2 wt. %.

In a second aspect, a dry electrode film of an energy storage device isdisclosed. The dry electrode film includes 90 wt. % to about 99 wt. % ofa dry active material, and at most about 2 wt. % of a dry binder,wherein the dry electrode film is free-standing.

All of these embodiments are intended to be within the scope of theinvention herein disclosed. These and other embodiments of the presentinvention will become readily apparent to those skilled in the art fromthe following detailed description of the preferred embodiments havingreference to the attached figures, the invention not being limited toany particular preferred embodiment(s) disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an embodiment of an energy storage device comprising areduced binder content.

FIG. 2 is a flow chart showing one embodiment of a process for preparingelectrode film mixtures.

FIGS. 3A-3F are line graphs showing voltage vs. specific capacity datafor various cathode active material films including PTFE as sole binderaccording to Example 3, as follows: FIG. 3A—NMC811, FIG. 3B—NMC111, FIG.3C—NMC532, FIG. 3D—NCA, FIG. 3E—NMC622, and FIG. 3F—sulfur-carboncomposite material.

FIG. 4 is a line graph of capacity retention vs. discharge C-ratesshowing comparative capacity retention data for a first cell having adry coated cathode and anode, and a second cell having a wet coatedcathode and anode, according to Example 4.

FIG. 5 is a line graph of capacity retention vs. discharge C-ratesshowing capacity retention data at a 2C discharge rate for five cellshaving NMC111 as cathode active material, according to Example 5.

FIG. 6 is a line graph of capacity retention vs. number of cyclesshowing cycling performance data for cells having dry electrodes cycledat 100% depth of discharge (DOD) using constant current charge anddischarge rates, according to Example 6.

FIGS. 7A-7D depict line graphs of voltage of cathodes vs. specificcapacity with high active loadings according to Formula 1 (FIG. 7A),Formula 2 (FIG. 7B), Formula 3 (FIG. 7C) and Formula 4 (FIG. 7D) ofExample 7.

DETAILED DESCRIPTION

Various embodiments of materials and methods for reduced binder contentand/or reduced damage active materials electrode film mixtures,electrode films, and energy storage devices incorporating the electrodefilms are described.

Damaged electrode active materials are thought to contribute to a numberof processes that result in deterioration of energy storage deviceperformance. Steps employed in typical dry electrode fabricationtechniques generally include high shear, high pressure, and/or highvelocity processing steps performed on all the dry electrode binder andactive materials. Such high shear processing may damage the electrodeactive materials, and thus contribute to deterioration of deviceperformance once the raw material is formed into an electrode within anenergy storage device. Over the life of an energy storage device,deterioration of device performance may manifest as reduced storagecapacity, capacitance fade, increased equivalent series resistance (ESR)of the device, self-discharge, pseudocapacity, and/or gas formation.Active materials having reduced damage may improve one or more of thesecharacteristics of an operating device.

One embodiment is a method of making an electrode comprising at leasttwo steps. First, an active material mixture is prepared. The activematerial mixture generally includes a porous carbon, an active materialand, optionally, an additive such as a conductive additive. Thecomponents of the active material mixture are first combined and mixedthrough a relatively low shear, nondestructive process. Second, anelectrode film mixture is prepared. In this process, a binder suitablefor providing structure to a dry processed electrode film is combinedwith the active material mixture to form an electrode film mixture. Thebinder may be a fibrillizable binder, and may comprise, consistessentially, or consist of, polytetrafluoroethylene (PTFE). In oneembodiment, only a single, fibrillizable binder is included. Then, thebinder is mixed with the active material mixture through a relativelylow shear, nondestructive process to form an electrode film mixture.Optionally, an electrode film can then be formed from the electrode filmmixture, for example, by pressing or calendering. The use of such aprocess was found to improve the operating characteristics of the finalelectrode film.

The electrode film forming processes may be compatible with dryelectrode fabrication technology. In some embodiments, no solvents areused in any stage of the electrode film fabrication.

The processability of a self-supporting dry electrode film was found tobe dependent on the particle sizes of the constituent materials. Largerparticle sizes were found to allow a reduction in binder content, yetstill be capable of forming a free-standing dry electrode film.Specifically, in some embodiments, cathode active materials may compriseaverage (D₅₀) particle sizes of at least about or more than about 10 μm,for example, about 10-20 μm. In a further embodiment, the averagecathode active material particle size may be on the order of 1/10 theelectrode film thickness.

In one embodiment, the electrode films formed using materials andprocesses as described herein were found to tolerate lower binderloading than those formed using conventional dry electrode film formingprocesses. Thus, in some embodiments, a binder matrix sufficient toprovide a self-supporting electrode film can be provided with reducedbinder loading compared to a typical dry electrode process. In someembodiments, only a single binder is required to form a self-supportingdry electrode film.

In some embodiments, the active material may only require 3 passesthrough a calender to form a self-supporting dry film having a targetthickness.

Active materials as incorporated in energy storage device electrodefilms may have an intraparticle structure that is important forperformance in energy storage. For example, particles of cathode activematerials, for example lithium metal oxides such as NMC, may have aninternal structure. Such materials may be present as secondary particleaggregations of primary particles. The secondary particle aggregates maybe decomposed during fabrication of the electrode film. Decomposition isworsened in destructive, e.g., high shear, high pressure and/or highvelocity, processing, as has typically been used in dry electrode filmfabrication. In some embodiments, only nondestructive processing stepsare used in electrode film fabrication.

Embodiments allow nondestructively processed, for example, undamagedand/or pristine, active material particulates to be incorporated into anelectrode film mixture to yield an improved performance. Thus, electrodefilms incorporating reduced degradation bulk active material(s) areprovided. For example, cathode active materials may exhibit improvedperformance relative to applications where the active material isdamaged during processing.

As noted above, processing a mixture of binder and active material(s)may break the particles of active material(s). Reduced energy storageperformance may result from damage to cathode active materials, forexample, due to fissure formation and/or cracking in the activematerial, or separation of active material(s) from binder and/or from acurrent collector. The overall performance of the device may be reducedcompared to a device incorporating pristine active material(s). Thus,disclosed herein in some embodiments are materials and methods providingactive material(s) incurring reduced damage during fabrication.

Further disclosed herein in some embodiments are nondestructive methodsfor dry cathode electrode fabrication. The nondestructive method may becharacterized by low shear, low pressure and/or low velocity processes.Certain embodiments of energy storage devices may provide reduced damagecathode active materials following processing. For example,self-supporting electrode films including reduced damage cathode activematerial(s) are provided. In some embodiments, the cathode electrodefilm is a hybrid film including a capacitor active material such asactivated carbon, and a battery active material such as anelectrochemically active material. Examples of electrochemically activematerials include lithium metal oxides, lithium metal phosphates, andlithium sulfides, and cathode active materials described herein.

In some embodiments, the materials and methods may also permit freestanding cathode electrode film fabrication using only low shear,nondestructive processing steps. Some binders, such aspolytetrafluoroethylene (PTFE), can undergo fibrillization and enablethe manufacturing of self-standing films without the aid of a solvent.Manufacturing such films may require physical processing of the bulkbinder to create fine particles, which can undergo fibrillization tocreate a matrix suitable for providing structure to the electrode film.Typically, this binder processing has been performed by a milling orblending operation at high pressure and under high shear forces, and inthe presence of the electrode active material(s). The forces applied inprocessing the binder may alter the form of the active material(s) anddamage the surface of the active material(s). For example, the particlesof active material(s) may break, fuse, strip, or be chemically alteredduring such processing.

An electrode film formed using materials and processes as describedherein may exhibit improved performance relative to one formed usingtypical dry electrode film forming processes. For example, the firstcycle efficiency of a lithium ion battery including at least oneelectrode prepared using materials and processes may be improved. Forexample, first cycle columbic efficiency during electrochemical cyclingmay be improved. In some embodiments, an electrode film includes reducedbinder loading compared to one fabricated using a typical dry electrodeprocess, while mechanical strength of the electrode film is maintained.

Definitions

The terms “battery” and “capacitor” are to be given their ordinary andcustomary meanings to a person of ordinary skill in the art. The terms“battery” and “capacitor” are nonexclusive of each other. A capacitor orbattery can refer to a single electrochemical cell that may be operatedalone or as a component of a multi-cell system.

The voltage of an energy storage device is the operating voltage for asingle battery or capacitor cell. Voltage may exceed the rated voltageor be below the rated voltage under load, or according to manufacturingtolerances.

A “self-supporting” electrode film is an electrode film thatincorporates binder matrix structures sufficient to support the film orlayer and maintain its shape such that the electrode film or layer canbe free-standing. When incorporated in an energy storage device, aself-supporting electrode film or active layer is one that incorporatessuch binder matrix structures. Generally, and depending on the methodsemployed, such electrode films are strong enough to be employed inenergy storage device fabrication processes without any outsidesupporting elements, such as a current collector or other film. Forexample, a “self-supporting” electrode film can have sufficient strengthto be rolled, handled, and unrolled within an electrode fabricationprocess without other supporting elements. A dry electrode film, such asa cathode electrode film or an anode electrode film, may beself-supporting.

A “solvent-free” electrode film is an electrode film that contains nodetectable processing solvents, processing solvent residues, orprocessing solvent impurities. A dry electrode film, such as a cathodeelectrode film or an anode electrode film, may be solvent-free.

A “wet” electrode, “wet process” electrode, or slurry electrode, is anelectrode prepared by at least one step involving a slurry of activematerial(s), binder(s), and optionally additive(s). A wet electrode mayinclude processing solvents, processing solvent residues, and/orprocessing solvent impurities.

A “nondestructive” process is a process in which an electrode activematerial, including the surface of the electrode active material, is notsubstantially modified during the process. Thus, the analyticalcharacteristics and/or performance in an application, such asincorporation in an energy storage device, of the active material, areidentical or nearly identical to those which have not undergone theprocess. For example, a coating on the active material may beundisturbed or substantially undisturbed during the process. Anon-limiting example of a nondestructive process is “nondestructivelymixing or blending,” or jet milling at a reduced pressure, increasedfeed rate, decreased velocity (e.g., blender speed), and/or change inother process parameter(s) such that the shear imparted upon an activematerial remains below a threshold at which the analyticalcharacteristics and/or performance of the active material would beadversely affected, when implemented into an energy storage device. Oneexample of an effective non-destructive mixing process is through theuse of a blade type mixer with a tip speed ranging from about 10meters/min to about 40 meters/min. A “nondestructive” process can bedistinguished from a high shear process which substantially modifies anelectrode active material, such as the surface of an electrode activematerial, and substantially affects the analytical characteristicsand/or the performance of the active material. For example, high shearblending or high shear jet milling can have detrimental effects on thesurface of an electrode active material. A high shear process may beimplemented, at the detriment to the active material surfacecharacteristics, to provide other benefits, such as fibrillization ofbinder material, or otherwise forming a binder/active material matrix toassist in forming a self-supporting electrode film. Embodiments hereinmay provide similar benefits, while avoiding the detrimental effects ofexcessive use of high shear processes. In general, the nondestructiveprocesses herein are performed at one or more of a higher feed rate,lower velocity, and/or lower pressure, resulting in a lower shearprocess than the more destructive processes that will otherwisesubstantially modify an electrode active material, and thus affectperformance.

The term “binder loading” refers to the mass of binder relative to themass of the final electrode film mixture. Binder loading can beexpressed with respect to a single binder, or a “total binder loading”which is the sum of the mass of all types of binders relative to themass of the final electrode film mixture.

Self-Supporting Electrode Films Having Reduced Binder Content

In some embodiments, compositions and methods for electrode filmscharacterized by reduced binder content are described. Generally, anactive material mixture is prepared by combining a cathode activematerial, a porous carbon, and optionally a conductive additive. Themixing of active material and porous carbon and optionally conductiveadditive can be by a method provided herein, or by any suitable method.The combining may be by a nondestructive process. The nondestructivemixing may comprise blending, tumbling, or acoustic mixing. The activematerial mixture may then be mixed with a binder to form an electrodefilm mixture. The mixing may be by a nondestructive process. Theelectrode film mixture may then be calendered to form a free-standingelectrode film. Fewer passes through a calender may be needed tofabricate a dry self-supporting electrode film as provided herein, ascompared to typical dry electrode fabrication methods. In someembodiments, a dry free-standing electrode film suitable for use in anenergy storage device is produced after 2, 3, 4, or 5 passes through acalender. In further embodiments, a dry free standing electrode filmsuitable for use in an energy storage device is produced after 3 passesthrough a calender.

In one embodiment, the self-supporting dry electrode film may compriseparticles having predetermined particle sizes. Larger particle sizesrelative to typical dry cathode electrode films were found in someembodiments to allow a reduction in binder content of a free-standingdry electrode film. In some embodiments, the cathode active materialparticles may on average have a longest dimension of about 8 μm, about 9μm, about 10 μm, about 12 μm, about 14 μm, about 16 μm, about 18 μm,about 20 μm, about 25 μm, or any range of values therebetween. Infurther embodiments the cathode active material particles may compriselithium nickel manganese cobalt oxide (NMC), lithium manganese oxide(LMO), lithium iron phosphate (LFP), lithium cobalt oxide (LCO), lithiumtitanate (LTO), lithium nickel cobalt aluminum oxide (NCA), or a cathodeactive material. In a still further embodiment, the cathode activematerial particles may comprise secondary particles including aggregatedprimary particles. In some embodiments, a cathode electrode filmincluding substantially pristine or substantially intact secondaryparticle aggregates of a cathode active material is provided. Thecathode active materials may be combined in a hybrid electrode film withcapacitive active materials.

An NMC component of the cathode active material may comprise varyingcompositions of its constituent elements. The NMC may comprise nickel,manganese, and cobalt in varying proportions. Some embodiments provideNMC622, which comprises nickel, manganese, and cobalt in a molar ratioof about 6:2:2, respectively. Some embodiments provide NMC111, whichcomprises nickel, manganese, and cobalt in a molar ratio of about 1:1:1,respectively. Some embodiments provide NMC532, which comprises nickel,manganese, and cobalt in a molar ratio of about 5:3:2, respectively.Some embodiments provide NMC811, which comprises nickel, manganese, andcobalt in a molar ratio of about 8:1:1, respectively. In someembodiments, the NMC may include about 5-10 wt % lithium, about 15-50 wt% nickel, about 5-20 wt % manganese, and about 5-20 wt % cobalt. Someembodiments provide NMC, including about 5-10 wt % lithium, about 15-50wt % nickel, about wt % manganese, about 5-20 wt % cobalt, about 25-40wt % oxygen, and trace impurities, wherein the percentages of lithium,nickel, manganese, cobalt, and oxygen sum to about 100 wt %.

The amounts of binder material and cathode active material can beadjusted. For example, the cathode electrode film can include about 95%cathode active material and 3% binder, or 95% cathode active materialand 2% binder. In another example, the cathode electrode film caninclude at or about 97% cathode active material and at or about 2% or1.75% binder. In another example, the cathode electrode film can includeat or about 98% cathode active material and at or about 1.25% binder.The remaining mass of the electrode may be made up of, for example,porous carbon and/or a conductive additive. The electrode film may havethe same amounts of cathode active material(s) and binder as theelectrode film mixture from which it is fabricated. In some embodiments,a cathode electrode film can comprise about weight %, about 92 weight %,about 94 weight %, about 95 weight %, about 96 weight %, about 97 weight%, about 98 weight % or about 99 weight % of active material, or anyrange of values therebetween. In certain embodiments, the cathode activematerial may be NMC or LFP. In some embodiments, the cathode electrodefilm can comprise up to about 8 weight % of the porous carbon material,including about 7 weight %, about 5 weight %, about 3 weight %, about 2weight %, or about 1 weight %, or any range of values therebetween. Incertain embodiments, the porous carbon material may be activated carbon.In some embodiments, the cathode electrode film comprises up to about 5weight %, including about 1 weight %, about 2 weight %, about 3 weight%, about 4 weight %, or about 5 weight %, of the conductive additive. Incertain embodiments, the conductive additive may be a conductive carbon,such as a carbon black.

In one embodiment, the cathode electrode film may incorporate lowerbinder loading than a film formed using typical dry electrode filmforming processes. In some embodiments, only a single binder at a lowbinder loading is needed to form a self-supporting dry electrode film.In a particular embodiment, the single binder is PTFE. In variousembodiments, the electrode film mixture, and/or electrode film, can havea binder loading of 1%, 1.5%, 2%, 2.5%, 3% or 5% by mass, or any rangeof values therebetween. In certain embodiments, the binder loading isabout 1.5 to about 3%. In certain embodiments, the cathode electrodefilm does not include PVDF.

Generally, the binder comprises a fibrillizable binder. Thefibrillizable binder may comprise, consist essentially, or consist ofPTFE. In some embodiments, an additional binder component may beincluded in the electrode film. In further embodiments, the binderincludes PTFE and a polyolefin, poly(ethylene oxide) (PEO),poly(phenylene oxide) (PPO), polyethylene-block-poly(ethylene glycol),polydimethylsiloxane (PDMS), polydimethylsiloxane-coalkylmethylsiloxane,co-polymers thereof, and/or admixtures thereof. In some embodiments, theone or more polyolefins can include polyethylene (PE), polypropylene(PP), polyvinylidene fluoride (PVDF), co-polymers thereof, and/ormixtures thereof. The binder can include a cellulose, for example,carboxymethylcellulose (CMC). In some embodiments, the binder particlesmay have selected sizes. In some embodiments, the binder particles maybe about 50 nm, about 100 nm, about 150 nm, about 200 nm, about 250 nm,about 300 nm, about 350 nm, about 400 nm, about 450 nm, about 500 nm,about 1 μm, about 10 μm, about 50 μm, about 100 μm, or any range ofvalues therebetween.

In some embodiments, the electrode film fabrication process comprisescombining a cathode active material, activated carbon, and a conductivecarbon additive, to form an active material mixture, and then mixingwith the active material mixture a binder comprising, consistingessentially, or consisting of PTFE to form an electrode film mixture.The active material mixture and PTFE can be mixed together first byselecting a mixing technique that will effectively mix and disperse thetwo components without damaging the cathode active material(s). Theelectrode film mixture is then calendered to form a free standingelectrode film. In certain embodiments, an electrode film fabricated bythe processes disclosed herein comprises a self-supporting cathodeelectrode film. In some embodiments, an electrode film fabricated by theprocesses disclosed herein comprises a self-supporting negative (anode)electrode film. The processes herein may be beneficial towardsimplementation with a cathode, because cathode active materials aresusceptible to particle degradation during processing.

In some embodiments, the electrode film mixture can be formed by a highshear and/or high pressure process. The high shear and/or high pressureprocess may include jet-milling. The processing time and/or feed rategenerally will have an effect on the final particle size of the binderand/or active material(s). For example, a longer time and/or slower feedrate may produce smaller particles.

In some embodiments, the electrode film mixture is subjected to one ormore dry electrode process(es), such as that described in U.S. PatentPublication No. 2015/0072234. In some embodiments, a dry electrode isprovided, wherein the dry electrode is free from processing contaminantssuch as solvents, and wherein the dry electrode is prepared by themethods and materials provided herein.

In further embodiments, an electrode fabricated using the materials andmethods described herein can be characterized by improved performance.The improved performance may be due to, for example, increased firstcycle efficiency. In some embodiments, the first cycle efficiency of anelectrode fabricated by the materials and methods provided herein ismore than about 85%. In further embodiments, the first cycle efficiencyis about 86%, about 87%, about 88%, about 89% about 90%, about 91%,about 92%, about 93%, about 94%, about 95%, or any range of valuestherebetween, and may be, for example, within a range of about 90 toabout 92% or about 90 to about 94%.

An energy storage device described herein may be characterized byreduced rise in equivalent series resistance over the life of thedevice, which may provide a device with increased power density over thelife of the device. In some embodiments, energy storage devicesdescribed herein may be characterized by reduced loss of capacity overthe life of the device. Further improvements that may be realized invarious embodiments include improved cycling performance, includingimproved storage stability during cycling, power delivery, and reducedcapacity fade. In some embodiments, capacity retention is at least 75%,at least 80%, at least 85%, or at least 90% of original capacity after2000 cycles. In further embodiments, capacity at a C-rate of 2 is atleast 75%, at least 80%, at least 85%, or at least 90% of capacity at aC-rate of 0.1. Some embodiments provide dry electrode full cells havingcapacity at a C-rate of 1 that is at least 10%, at least 20%, or atleast 30% higher than a wet electrode full cell having substantially thesame active material loading.

The materials and methods provided herein can be implemented in variousenergy storage devices. An energy storage device can be a capacitor, alithium ion capacitor (LIC), an ultracapacitor, a battery, or a hybridenergy storage device and/or a hybrid cell, combining aspects of two ormore of the foregoing. In preferable embodiments, the device is abattery. The energy storage device can be characterized by an operatingvoltage. In some embodiments, an energy storage device described hereincan have an operating voltage of about 0 V to about 4.5 V. In furtherembodiments, the operating voltage can be about 2.7 V to about 4.2 V,about 3.0 to about 4.2 V, or any range of values therebetween.

An energy storage device may include one or more electrodes. Theelectrode film can be formed from a mixture of one or more binders andone or more active electrode material(s). It will be understood that anelectrode film can be used in various embodiments with any of a numberof energy storage devices and systems, such as one or more batteries,capacitors, capacitor-battery hybrids, fuel cells, or other energystorage systems or devices, and combinations thereof. In someembodiments, an electrode film described herein may be a component of alithium ion capacitor, a lithium ion battery, an ultracapacitor, or ahybrid energy storage device combining aspects of two or more of theforegoing.

An energy storage device can be of any suitable configuration, forexample planar, spirally wound, button shaped, or pouch. An energystorage device can be a component of a system, for example, a powergeneration system, an uninterruptible power source systems (UPS), aphoto voltaic power generation system, an energy recovery system for usein, for example, industrial machinery and/or transportation. An energystorage device may be used to power various electronic device and/ormotor vehicles, including hybrid electric vehicles (HEV), plug-in hybridelectric vehicles (PHEV), and/or electric vehicles (EV).

FIG. 1 shows a side cross-sectional schematic view of an example of anenergy storage device 100 having an electrode film having a reducedbinder content. The energy storage device 100 may be classified as, forexample, a capacitor, a battery, a capacitor-battery hybrid, or a fuelcell.

The device can have a first electrode 102, a second electrode 104, and aseparator 106 positioned between the first electrode 102 and secondelectrode 104. Either or both of the electrodes 102 and 104 may befabricated according to the materials and processes provided herein. Thefirst electrode 102 and the second electrode 104 may be placed adjacentto respective opposing surfaces of the separator 106. The energy storagedevice 100 may include an electrolyte 118 to facilitate ioniccommunication between the electrodes 102, 104 of the energy storagedevice 100. For example, the electrolyte 118 may be in contact with thefirst electrode 102, the second electrode 104 and the separator 106. Theelectrolyte 118, the first electrode 102, the second electrode 104, andthe separator 106 may be received within an energy storage devicehousing 120. One or more of the first electrode 102, the secondelectrode 104, and the separator 106, or constituent thereof, maycomprise porous material. The pores within the porous material canprovide containment for and/or increased surface area for reactivitywith an electrolyte 118 within the housing 120. The energy storagedevice housing 120 may be sealed around the first electrode 102, thesecond electrode 104 and the separator 106, and may be physically sealedfrom the surrounding environment.

In some embodiments, the first electrode 102 can be an anode (the“negative electrode”) and the second electrode 104 can be the cathode(the “positive electrode”). The separator 106 can be configured toelectrically insulate two electrodes adjacent to opposing sides of theseparator 106, such as the first electrode 102 and the second electrode104, while permitting ionic communication between the two adjacentelectrodes. The separator 106 can comprise a suitable porous,electrically insulating material. In some embodiments, the separator 106can comprise a polymeric material. For example, the separator 106 cancomprise a cellulosic material (e.g., paper), a polyethylene (PE)material, a polypropylene (PP) material, and/or a polyethylene andpolypropylene material.

Generally, the first electrode 102 and second electrode 104 eachcomprise a current collector and an electrode film. Electrodes 102 and104 comprise electrode films 112 and 114, respectively. Electrode films112 and 114 can have any suitable shape, size and thickness. Forexample, the electrode films can have a thickness of about 30 microns(μm) to about 250 microns, for example, about 50 microns, about 100microns, about 150 microns, about 200 microns, about 250 microns, or anyrange of values therebetween. The electrode films can comprise one ormore materials, or be fabricated using processes, provided herein. Insome embodiments, at least one of electrode films 112 and 114 caninclude an electrode film mixture comprising binder material and acathode active material. As illustrated, the second electrode film 114comprises cathode active material particles 122 and binder materialparticles 124, and a reduced binder content. In some embodiments, theactive material can be a cathode active material. In some embodiments,the cathode active material can be, for example, a metal oxide, metalsulfide, a sulfur-carbon composite, or a lithium metal oxide. Thelithium metal oxide can be, for example, a lithium nickel manganesecobalt oxide (NMC), a lithium manganese oxide (LMO), a lithium ironphosphate (LFP), a lithium cobalt oxide (LCO), a lithium titanate (LTO),lithium nickel manganese oxide (LNMO) and/or a lithium nickel cobaltaluminum oxide (NCA). In some embodiments, cathode active materials canbe comprised of, for example, a layered transition metal oxide (such asLiCoO2 (LCO), Li(NiMnCo)O2 (NMC) and/or LiNi0.8Co0.15Al0.05O2 (NCA)), aspinel manganese oxide (such as LiMn2O4 (LMO) and/or LiMn1.5Ni0.5O4(LMNO)) or an olivine (such as LiFePO4). The cathode active material cancomprise sulfur or a material including sulfur, such as lithium sulfide(Li2S), or other sulfur-based materials, or a mixture thereof. In someembodiments, the cathode film comprises a sulfur or a material includingsulfur active material at a concentration of at least 50 wt %. In someembodiments, the cathode film comprising a sulfur or a materialincluding sulfur active material has an area-normalized specificcapacity (i.e., areal capacity) of at least 10 mAh/cm2. In someembodiments, the cathode film comprising a sulfur or a materialincluding sulfur active material has an electrode film density of 1g/cm3. In some embodiments, the cathode film comprising a sulfur or amaterial including sulfur active material further comprises a binder.

The at least one active material may include one or more carbonmaterials. The carbon materials may be selected from, for example,graphitic material, graphite, graphene-containing materials, hardcarbon, soft carbon, carbon nanotubes, porous carbon, conductive carbon,or a combination thereof. Activated carbon can be derived from a steamprocess or an acid/etching process. In some embodiments, the graphiticmaterial can be a surface treated material. In some embodiments, theporous carbon can comprise activated carbon. In some embodiments, theporous carbon can comprise hierarchically structured carbon. In someembodiments, the porous carbon can include structured carbon nanotubes,structured carbon nanowires and/or structured carbon nanosheets. In someembodiments, the porous carbon can include graphene sheets. In someembodiments, the porous carbon can be a surface treated carbon. Inpreferred embodiments, the active material comprises, consistsessentially of, or consists of graphite.

The first electrode film 112 and/or the second electrode film 114 mayalso include one or more binders. In some embodiments, the firstelectrode film 112 and/or the second electrode film 114 may include asingle binder. In some embodiments, the binder can include one or morepolymers. In some embodiments, the binder can include one or morefibrillizable binder components. The binder component may be fibrillizedto provide a plurality of fibrils, the fibrils providing desiredmechanical support for one or more other components of the film. In someembodiments, a binder component can include one or more of a variety ofsuitable fibrillizable polymeric materials.

Generally, the electrode films described herein can be fabricated usinga modified dry fabrication process. For example, some steps may be asdescribed in U.S. Patent Publication No. 2005/0266298 and U.S. PatentPublication No. 2006/0146479. These, and any other references toextrinsic documents herein, are hereby incorporated by reference intheir entirety. A dry fabrication process can refer to a process inwhich no or substantially no solvents are used in the formation of anelectrode film. For example, components of the electrode film, includingcarbon materials and binders, may comprise dry particles. The dryparticles for forming the electrode film may be combined to provide adry particles electrode film mixture. In some embodiments, the electrodefilm may be formed from the dry particle electrode film mixture suchthat weight percentages of the components of the electrode film andweight percentages of the components of the dry particles electrode filmmixture are substantially the same. In some embodiments, the electrodefilm formed from the dry particle electrode film mixture using the dryfabrication process may be free from, or substantially free from, anyprocessing additives such as solvents and solvent residues resultingtherefrom. In some embodiments, the resulting electrode films areself-supporting electrode films formed using the dry process from thedry particle mixture. In some embodiments, the resulting electrode filmsare free-standing electrode films formed using the dry process from thedry particle mixture. A process for forming an electrode film caninclude fibrillizing the fibrillizable binder component(s) such that theelectrode film comprises fibrillized binder. In further embodiments, afree-standing electrode film may be formed in the absence of a currentcollector. In still further embodiments, an electrode film may comprisea fibrillized polymer matrix such that the electrode film isself-supporting.

With continued reference to FIG. 1 , the first electrode 102 and thesecond electrode 104 include a first current collector 108 in contactwith first electrode film 112, and a second current collector 110 incontact with the second electrode film 114, respectively. The firstcurrent collector 108 and the second current collector 110 mayfacilitate electrical coupling between each corresponding electrode filmand an external electrical circuit (not shown). The first currentcollector 108 and/or the second current collector 110 can comprise oneor more electrically conductive materials, and have any suitable shapeand size selected to facilitate transfer of electrical charge betweenthe corresponding electrode and an external circuit. For example, acurrent collector can include a metallic material, such as a materialcomprising aluminum, nickel, copper, rhenium, niobium, tantalum, andnoble metals such as silver, gold, platinum, palladium, rhodium, osmium,iridium and alloys and combinations of the foregoing. For example, thefirst current collector 108 and/or the second current collector 110 cancomprise an aluminum foil. The aluminum foil can have a rectangular orsubstantially rectangular shape sized to provide transfer of electricalcharge between the corresponding electrode and an external electricalcircuit.

In some embodiments, the energy storage device 100 is a lithium ionbattery or hybrid energy storage device including a cathode comprising acathode active material. In some embodiments, the lithium ion battery isconfigured to operate at about 2.5 to 4.5 V, or 2.7 to 4.2 V.

Technologies described herein may be used separately or in combinationin an energy storage device to enable operation under the selectedconditions.

In some embodiments, energy storage device 100 can be a lithium ionenergy storage device such as a lithium ion capacitor, a lithium ionbattery, or a hybrid lithium ion device. Generally, a lithium ion energystorage device comprises a cathode including a lithium-containingcathode active material, and an anode electrode film suitable forinteracting with lithium ions.

In some embodiments, an anode electrode film may comprise an activematerial, a binder, and optionally a conductive additive. In someembodiments, the conductive additive may comprise a conductive carbonadditive, such as carbon black. In some embodiments, the active materialof the anode may comprise a graphitic carbon, synthetic graphite,natural graphite, hard carbon, soft carbon, graphene, mesoporous carbon,silicon, silicon oxides, tin, tin oxides, germanium, lithium titanate,mixtures, or composites of the aforementioned materials. In someembodiments, an anode electrode film can include about 80 weight % toabout 98 weight % of the active material, including about 90 weight % toabout 98 weight %, or about 94 weight % to about 97 weight %. In someembodiments, the anode electrode film comprises up to about 5 weight %,including about 1 weight % to about 3 weight %, of the conductiveadditive. In some embodiments, the anode electrode film comprises up toabout 20 weight % of the binder, including about 1.5 weight % to 10weight %, about 1.5 weight % to 5 weight %, or about 3 weight % to 5weight %. In some embodiments, the anode electrode film comprises about4 weight % binder. In some embodiments, the anode film may not include aconductive additive.

In some embodiments, the electrode film, for example, anode electrodefilm, of a lithium ion energy storage device electrode comprises acarbon configured to reversibly intercalate lithium ions. In someembodiments, the lithium intercalating carbon is selected from agraphitic carbon, graphite, hard carbon, soft carbon and combinationsthereof. For example, the electrode film of the electrode can include abinder material, one or more of graphitic carbon, graphite,graphene-containing carbon, hard carbon and soft carbon, and anelectrical conductivity promoting material. In some embodiments, anelectrode is mixed with lithium metal and/or lithium ions. The anodeelectrode film may be a dry self-supporting electrode film.

Some embodiments include an electrode, such as an anode and/or acathode, having one or more electrode films comprising a polymericbinder material. In some embodiments, the binder may comprise PTFE. Infurther embodiments, the binder may comprise PTFE and one or moreadditional binder components. In some embodiments, the binder maycomprise one or more polyolefins and/or co-polymers thereof, and PTFE.In some embodiments, the binder may comprise a PTFE and one or more of acellulose, a polyolefin, a polyether, a precursor of polyether, apolysiloxane, co-polymers thereof, and/or admixtures thereof. In someembodiments, the binder can include branched polyethers,polyvinylethers, co-polymers thereof, and/or the like. The binder caninclude co-polymers of polysiloxanes and polysiloxane, and/orco-polymers of polyether precursors. For example, the binder can includepoly(ethylene oxide) (PEO), poly(phenylene oxide) (PPO),polyethylene-block-poly(ethylene glycol), polydimethylsiloxane (PDMS),polydimethylsiloxane-coalkylmethylsiloxane, co-polymers thereof, and/oradmixtures thereof. In some embodiments, the one or more polyolefins caninclude polyethylene (PE), polypropylene (PP), polyvinylidene fluoride(PVDF), co-polymers thereof, and/or mixtures thereof. The binder caninclude a cellulose, for example, carboxymethylcellulose (CMC). Anadmixture of polymers may comprise interpenetrating networks of theaforementioned polymers or co-polymers.

The binder may include various suitable ratios of the polymericcomponents. For example, PTFE can be up to about 100 weight % of thebinder, for example, from about 20 weight % to about 95 weight %, about20 weight % to about 90 weight %, including about 20 weight % to about80 weight %, about 30 weight % to about 70 weight %, or about 30 weight% to about 50 weight %. In further embodiments, the binders can comprisePTFE, CMC, and PVDF as binders. In certain embodiments, the electrodefilm can comprise 2 weight % PTFE, 1 weight % CMC, and 1 weight % PVDF.For example, the binder mixture can include a mass of PTFE which is 50%of the total binder content of the electrode film, and 2% of the totalmass of the electrode film.

In further embodiments, the energy storage device 100 is charged with asuitable lithium-containing electrolyte. For example, device 100 caninclude a lithium salt, and a solvent, such as a non-aqueous or organicsolvent. Generally, the lithium salt includes an anion that is redoxstable. In some embodiments, the anion can be monovalent. In someembodiments, a lithium salt can be selected from hexafluorophosphate(LiPF₆), lithium tetrafluoroborate (LiBF₄), lithium perchlorate(LiClO₄), lithium bis(trifluoromethansulfonyl)imide (LiN(SO₂CF₃)₂),lithium trifluoromethansulfonate (LiSO₃CF₃), and combinations thereof.In some embodiments, the electrolyte can include a quaternary ammoniumcation and an anion selected from the group consisting ofhexafluorophosphate, tetrafluoroborate and iodide. In some embodiments,the salt concentration can be about 0.1 mol/L (M) to about 5 M, about0.2 M to about 3 M, or about 0.3 M to about 2 M. In further embodiments,the salt concentration of the electrolyte can be about 0.7 M to about 1M. In certain embodiments, the salt concentration of the electrolyte canbe about 0.2 M, about 0.3 M, about 0.4 M, about 0.5 M, about 0.6 M,about 0.7 M, about 0.8 M. about 0.9 M, about 1 M, about 1.1 M, about 1.2M, or any range of values therebetween.

In some embodiments, an energy storage device can include a solvent. Thesolvent may be in liquid phase under the nominal operating conditions ofthe device. A solvent need not dissolve every component, and need notcompletely dissolve any component, of the electrolyte. In furtherembodiments, the solvent can be an organic solvent. In some embodiments,a solvent can include one or more functional groups selected fromcarbonates, ethers and/or esters. In some embodiments, the solvent cancomprise a carbonate. In further embodiments, the carbonate can beselected from cyclic carbonates such as, for example, ethylene carbonate(EC), propylene carbonate (PC), vinyl ethylene carbonate (VEC), vinylenecarbonate (VC), fluoroethylene carbonate (FEC), and combinationsthereof, or acyclic carbonates such as, for example, dimethyl carbonate(DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), andcombinations thereof. In certain embodiments, the electrolyte cancomprise LiPF₆, and one or more carbonates.

In some embodiments, the active material includes a treated carbonmaterial, where the treated carbon material includes a reduction in anumber of hydrogen-containing functional groups, nitrogen-containingfunctional groups and/or oxygen-containing functional groups, asdescribed in U.S. Patent Publication No. 2014/0098464. For example, thetreated carbon particles can include a reduction in a number of one ormore functional groups on one or more surfaces of the treated carbon,for example about 10% to about 60% reduction in one or more functionalgroups compared to an untreated carbon surface, including about 20% toabout 50%. The treated carbon can include a reduced number ofhydrogen-containing functional groups, nitrogen-containing functionalgroups, and/or oxygen-containing functional groups. In some embodiments,the treated carbon material comprises functional groups less than about1% of which contain hydrogen, including less than about 0.5%. In someembodiments, the treated carbon material comprises functional groupsless than about 0.5% of which contains nitrogen, including less thanabout 0.1%. In some embodiments, the treated carbon material comprisesfunctional groups less than about 5% of which contains oxygen, includingless than about 3%. In further embodiments, the treated carbon materialcomprises about 30% fewer hydrogen-containing functional groups than anuntreated carbon material.

In some embodiments, a method for fabricating an energy storage deviceis provided. FIG. 2 depicts an embodiment of a method 200 for preparingan electrode film mixture for use in an energy storage device. In step202, an active material, a porous carbon, and optionally a conductiveadditive are combined to form an active material mixture. In step 204,the active material mixture is mixed with a binder in a low shearprocess to form an electrode film mixture. In step 206, the electrodefilm mixture is calendered to form a free standing electrode film.Generally, step 206 results in a binder matrix within the electrode filmsuch that the electrode film is self-supporting. In step 208, the freestanding electrode film is optionally laminated to a current collector.In some embodiments, each step of method 200 is a dry process step inwhich no solvents are used.

EXAMPLES Comparative Example 1

Activated carbon was combined with dry PVDF powder in a mass ratio of4:2 and the mixture was blended for 10 minutes. The resulting mixedpowder was jet-milled. NMC622, additional activated carbon, and carbonblack were added, and the resulting mixture was blended to a uniform tapdensity. The powder was combined with the jet-milled activatedcarbon/PVDF mixture, and the resulting mixture was blended for 5minutes. Finally, PTFE was added, and the mixture was blended for 10minutes. The final electrode film comprised 88:5:2:2:3 NMC622: activatedcarbon:carbon black:PVDF:PTFE. Thus, active material loading was 88%,and total binder loading was 5%.

Comparative Example 2

Activated carbon was combined with dry PVDF powder in a mass ratio of4:2 and the mixture was blended for 10 minutes. The resulting mixedpowder was jet-milled. NMC811, additional activated carbon, and carbonblack were added, and the resulting mixture was blended to a uniform tapdensity. The powder was combined with the jet-milled activatedcarbon/PVDF mixture, and the resulting mixture was blended for 5minutes. Finally, PTFE was added, and the mixture was blended for 10minutes and pressed on a 2-roll calender mill to form a free-standingfilm. The final electrode film comprised 92:3.3:1.5:1.7:1.5 NMC811:activated carbon:carbon black:PVDF:PTFE. Thus, active material loadingwas 92%, and total binder loading was 3.2%. The cathode film waslaminated on to a carbon coated aluminum foil to yield a dry coatedelectrode with loading weight of 16.6 mg/cm2 and thickness of 53microns. This electrode was evaluated against a lithium metal counterelectrode in a CR2032 coin cell. The first charge and discharge specificcapacity is measured at about 224 mAh/g and 202 mAh/g, respectively.

Example 1

NMC622 (Umicore), activated carbon (YP-17D, Kuraray), and conductivecarbon (carbon black, Ketjenblack ECP600JD, Lion Corp.) were combined,and the mixture was blended for 30 to 45 minutes at 3800 rpm. PTFE wasthen added, and the resulting mixture was blended for 20 to 25additional minutes at 3800 rpm at high shear. The final electrode filmcomprised 94:2:1:3 NMC622: activated carbon:conductive carbon:PTFE.Thus, active material loading was 94%, and total binder loading was 3%.

Example 2

A second electrode film was fabricated according to the method ofExample 1, but the final electrode film comprised 95:2:1:2 NMC622:activated carbon:conductive carbon:PTFE. Thus, active material loadingwas 95%, and total binder loading was 2%.

Data for the two electrode films of Examples 1 and 2 is provided inTable 1. The charge capacity, discharge capacity, and efficiency are forcathode half-cells of Example 1 and Example 2. In Table 1, the Gurleynumber indicates the time in seconds for 100 cc of air to pass through aone-square inch of membrane when a standard constant pressure of 60pounds per square inch is applied.

TABLE 1 Gurley Charge Discharge First Cycle Thickness Loading numbercapacity capacity Efficiency Example (μm) (mg/cm²) (sec) (mAh/g) (mAh/g)(%) 1 130-133 40 22-26 197 179 91 2 131-133 40 18-21 196 178 90.8

Example 3

Additional cathode electrode films were fabricated according to themethod of Example 1, but including various cathode active materials.PTFE was the sole binder in each electrode film. FIGS. 3A-3F providevoltage vs. specific capacity data for the various cathode electrodefilms, as follows: FIG. 3A—NMC811, FIG. 3B—NMC111, FIG. 3C—NMC532, FIG.3D—NCA, FIG. 3E—NMC622, and FIG. 3F—sulfur-carbon composite. As seen inFIGS. 3A-3E, each of the NMC dry coated electrodes exhibited dischargeprofiles with stable voltage plateaus at the end of the dischargeprocess to yield their corresponding designed specific capacityaccounting for active material (NCA specific charge capacity is about219 mAh/g and specific discharge capacity is about 195-200 mAh/g; NMC622specific charge capacity is about 200 mAh/g and specific dischargecapacity is about 175 mAh/g; NMC811 specific capacity is about 195-210mAh/g), indicating that almost all the active material particles wereaccessible in each case.

Example 4

Two cells, a first cell electrodes made with a dry process, and a secondcell having electrodes made through a wet process, were prepared. Thecathodes of both cells included NMC111 as the cathode active materialand graphite as the anode active material, at the same concentrations ofactive materials. A constant current of 0.1 C was applied to charge thecell to 100% SOC prior to discharge. Discharge was conducted at variousC-rates. Under low constant current discharge, both coated electrodetypes yielded cell discharge capacity of 105 mAh, and the results wereused as a standard to normalize cell capacity. Electrode loading was 5mAh/cm² (cathodes at 36 mg/cm²) for each cell, and cut-off voltage was4.2V and 2.8V for charge and discharge, respectively. Comparativecapacity retention data for the dry coated and wet coated cells isprovided in FIG. 4 . The dry process electrode film had better capacityat high discharge rates (up to 1 C as measured).

Example 5

Five additional cells were fabricated, each including NMC111 cathodeelectrode films made with a dry process. Each cell included dry coatedNMC111 (94 wt. % loading) cathode and graphite (96 wt. % loading) anodeelectrodes, in a pouch cell configuration. NMC111 electrode loading was27 mg/cm² (areal capacity 4 mAh/cm²). The cell was charged to 4.2V atconstant current followed by constant voltage at 4.2V and discharged to2.8V. FIG. 5 provides rate performance data. Capacity retention for eachof the five cells incorporating dry coated electrodes was above 90% at a2C discharge rate.

A higher rate capability was found in the dry coated electrodes, as seenin FIG. 5 . The high energy density and power capability are attributedto low charge transfer and contact resistance in the dry coatedelectrodes.

Example 6

Cells having electrodes made by a dry process were cycled at 100% depthof discharge (DOD) using constant current charge and discharge rates of0.5 C/1 C, respectively. Cycling performance was measured on anNMC111/graphite cell including dry coated electrodes in a pouch cellformat. Electrode loading was 4 mAh/cm². Cut-off voltage was 4.2 V and2.7 V for charge and discharge, respectively. It can be observed in FIG.6 that the cell delivered more than 85% (nearly 90%) of its initialcapacity after 2000 cycles.

Example 7

Dry cathode films with low binder content of Formulas 1-4 are shown inTable 2. Voltage vs. specific capacities of cathode half-cells made fromFormulas 1-4 were measured as shown in FIGS. 7A-7D, and their dischargecapacities and efficiencies are shown in Table 2. Formulas 1-3 wereprepared by mixing NMC811, activated carbon and carbon black by highspeed blending for about 10 min to create a densified powder mixture.PTFE binder was added to densified powder mixture and then blended atmedium speed for additional 10 min. Formula 4 was prepared in a similarprocess to Formulas 1-3, however the film was prepared with NMC622,activated carbon and carbon black were non-destructively mixed using anresonant acoustic mixer.

TABLE 2 Active Activated Carbon Discharge First Cycle Formula MaterialCarbon Black Binder Loading Capacity Efficiency 1 98 wt % 0.25 wt % 0.5wt % 1.25 wt % 38.4 mg/cm2 194 mAh/g 87.1% NMC811 PTFE 2 97 wt %  0.5 wt% 0.5 wt %   2 wt % 31.4 mg/cm2 214 mAh/g 93.6% NMC811 PTFE 3 97 wt %0.75 wt % 0.5 wt % 1.75 wt % 33.2 mg/cm2 214 mAh/g 92.7% NMC811 PTFE 497 wt % 0.75 wt % 0.5 wt % 1.75 wt % 35.7 mg/cm2 179 mAh/g 91.1% NMC622PTFE

While certain embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms. Furthermore, various omissions, substitutions and changes in thesystems and methods described herein may be made without departing fromthe spirit of the disclosure. The accompanying claims and theirequivalents are intended to cover such forms or modifications as wouldfall within the scope and spirit of the disclosure. Accordingly, thescope of the present inventions is defined only by reference to theappended claims.

Features, materials, characteristics, or groups described in conjunctionwith a particular aspect, embodiment, or example are to be understood tobe applicable to any other aspect, embodiment or example described inthis section or elsewhere in this specification unless incompatibletherewith. All of the features disclosed in this specification(including any accompanying claims, abstract and drawings), and/or allof the steps of any method or process so disclosed, may be combined inany combination, except combinations where at least some of suchfeatures and/or steps are mutually exclusive. The protection is notrestricted to the details of any foregoing embodiments. The protectionextends to any novel one, or any novel combination, of the featuresdisclosed in this specification (including any accompanying claims,abstract and drawings), or to any novel one, or any novel combination,of the steps of any method or process so disclosed.

Furthermore, certain features that are described in this disclosure inthe context of separate implementations can also be implemented incombination in a single implementation. Conversely, various featuresthat are described in the context of a single implementation can also beimplemented in multiple implementations separately or in any suitablesubcombination. Moreover, although features may be described above asacting in certain combinations, one or more features from a claimedcombination can, in some cases, be excised from the combination, and thecombination may be claimed as a subcombination or variation of asubcombination.

Moreover, while operations may be depicted in the drawings or describedin the specification in a particular order, such operations need not beperformed in the particular order shown or in sequential order, or thatall operations be performed, to achieve desirable results. Otheroperations that are not depicted or described can be incorporated in theexample methods and processes. For example, one or more additionaloperations can be performed before, after, simultaneously, or betweenany of the described operations. Further, the operations may berearranged or reordered in other implementations. Those skilled in theart will appreciate that in some embodiments, the actual steps taken inthe processes illustrated and/or disclosed may differ from those shownin the figures. Depending on the embodiment, certain of the stepsdescribed above may be removed, others may be added. Furthermore, thefeatures and attributes of the specific embodiments disclosed above maybe combined in different ways to form additional embodiments, all ofwhich fall within the scope of the present disclosure. Also, theseparation of various system components in the implementations describedabove should not be understood as requiring such separation in allimplementations, and it should be understood that the describedcomponents and systems can generally be integrated together in a singleproduct or packaged into multiple products. For example, any of thecomponents for an energy storage system described herein can be providedseparately, or integrated together (e.g., packaged together, or attachedtogether) to form an energy storage system.

For purposes of this disclosure, certain aspects, advantages, and novelfeatures are described herein. Not necessarily all such advantages maybe achieved in accordance with any particular embodiment. Thus, forexample, those skilled in the art will recognize that the disclosure maybe embodied or carried out in a manner that achieves one advantage or agroup of advantages as taught herein without necessarily achieving otheradvantages as may be taught or suggested herein.

Conditional language, such as “can,” “could,” “might,” or “may,” unlessspecifically stated otherwise, or otherwise understood within thecontext as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements, and/or steps. Thus, such conditional language is notgenerally intended to imply that features, elements, and/or steps are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or without userinput or prompting, whether these features, elements, and/or steps areincluded or are to be performed in any particular embodiment.

Conjunctive language such as the phrase “at least one of X, Y, and Z,”unless specifically stated otherwise, is otherwise understood with thecontext as used in general to convey that an item, term, etc. may beeither X, Y, or Z. Thus, such conjunctive language is not generallyintended to imply that certain embodiments require the presence of atleast one of X, at least one of Y, and at least one of Z.

Language of degree used herein, such as the terms “approximately,”“about,” “generally,” and “substantially” represent a value, amount, orcharacteristic close to the stated value, amount, or characteristic thatstill performs a desired function or achieves a desired result.

The scope of the present disclosure is not intended to be limited by thespecific disclosures of preferred embodiments in this section orelsewhere in this specification, and may be defined by claims aspresented in this section or elsewhere in this specification or aspresented in the future. The language of the claims is to be interpretedbroadly based on the language employed in the claims and not limited tothe examples described in the present specification or during theprosecution of the application, which examples are to be construed asnon-exclusive.

EMBODIMENTS

Various example embodiments are provided below.

1. A method of fabricating a dry electrode film of an energy storagedevice, comprising:

-   -   mixing an active material with a porous carbon material to form        a dry active material mixture;    -   mixing the dry active material mixture with a dry binder to form        a dry electrode film mixture; and    -   calendering the dry electrode film mixture to form a        free-standing dry electrode film with a binder loading of at        most about 2 wt. %.

2. The method of Embodiment 1, wherein calendering the dry electrodefilm mixture comprises at most three passes through a calender.

3. The method of any one of Embodiments 1 to 2, wherein at least one ofthe mixing of the active material and the porous carbon material and themixing of the dry active material mixture with a dry binder is performedby a non-destructive mixing process.

4. The method of Embodiment 3, wherein the non-destructively mixingprocess is a resonant acoustic mixing process.

5. The method of Embodiment 3, wherein the non-destructively mixingprocess is performed by a blade type mixer with a tip speed of about 10meters/min to about 40 meters/min.

6. The method of any one of Embodiments 1 to 2, wherein at least one ofthe mixing of the active material and the porous carbon material and themixing of the dry active material mixture with a dry binder is performedby a high shear process.

7. The method of Embodiment 6, wherein the high shear process comprisesa jet milling process.

8. A dry electrode film of an energy storage device, comprising:

-   -   about 90 wt. % to about 99 wt. % of a dry active material; and    -   at most about 2 wt. % of a dry binder, wherein the dry electrode        film is free-standing.

9. The dry electrode film of Embodiment 8, comprising about 95 wt. % toabout 98 wt. % of the dry active material.

10. The dry electrode film of any one of Embodiments 8 to 9, wherein thedry active material comprises dry active material particles with a D50particle size of at least about 10 μm.

11. The dry electrode film of Embodiment 10, wherein the dry activematerial particles have a D50 particle size of about 10 μm to about 20μm.

12. The dry electrode film of any one of Embodiments 8 to 11, whereinthe dry active material is selected from at least one of a metal oxide,metal sulfide, a sulfur-carbon composite, a lithium metal oxide and amaterial including sulfur.

13. The dry electrode film of any one of Embodiments 8 to 12, whereinthe electrode film comprises about 1 wt. % to about 2 wt. % of a drybinder.

14. The dry electrode film of any one of Embodiments 8 to 13, whereinthe dry binder consists essentially of a single dry binder.

15. The dry electrode film of any one of Embodiments 8 to 14, whereinthe dry binder comprises a dry fibrillizable binder.

16. The dry electrode film of Embodiment 15, wherein the dryfibrillizable binder comprises polytetrafluoroethylene (PTFE).

17. The dry electrode film of any one of Embodiments 8 to 16, whereinthe dry electrode film further comprises at most about 8 wt. % of aporous carbon material.

18. The dry electrode film of Embodiment 17, wherein the porous carbonmaterial comprises activated carbon.

19. The dry electrode film of any one of Embodiments 8 to 18, whereinthe dry electrode film further comprises at most about 5 wt. % of aconductive additive.

20. The dry electrode film of Embodiment 19, wherein the conductiveadditive comprises a conductive carbon material.

21. The dry electrode film of Embodiment 20, wherein the conductivecarbon material comprises carbon black.

22. An electrode comprising the dry electrode film of any one ofEmbodiments 8 to 21 in contact with a current collector.

23. A lithium ion battery comprising the electrode of Embodiment 22.

24. The lithium ion battery of Embodiment 23, having a first cycledevice efficiency of at least about 90%.

25. The lithium ion battery of any one of Embodiments 24, having a firstcycle device efficiency of about 90% to about 94%.

What is claimed is:
 1. A dry electrode film of an energy storage device,comprising: about 90 wt. % to about 99 wt. % of a dry active material;and at most 2 wt. % of a dry binder, wherein the dry electrode film isfree-standing.
 2. The dry electrode film of claim 1, comprising about 95wt. % to about 98 wt. % of the dry active material.
 3. The dry electrodefilm of claim 1, wherein the dry active material comprises dry activematerial particles with a D₅₀ particle size of at least about 10 μm. 4.The dry electrode film of claim 3, wherein the dry active materialparticles have a D₅₀ particle size of about 10 μm to about 20 μm.
 5. Thedry electrode film of claim 1, wherein the dry active material isselected from at least one of a metal oxide, metal sulfide, asulfur-carbon composite, a lithium metal oxide and a material includingsulfur.
 6. The dry electrode film of claim 1, wherein the electrode filmcomprises about 1 wt. % to 2 wt. % of a dry binder.
 7. The dry electrodefilm of claim 1, wherein the dry binder consists essentially of a singledry binder.
 8. The dry electrode film of claim 1, wherein the dry bindercomprises a dry fibrillizable binder.
 9. The dry electrode film of claim8, wherein the dry fibrillizable binder comprisespolytetrafluoroethylene (PTFE).
 10. The dry electrode film of claim 1,wherein the dry electrode film further comprises a porous carbonmaterial.
 11. The dry electrode film of claim 10, wherein the dryelectrode film comprises at most about 8 wt. % of the porous carbonmaterial.
 12. The dry electrode film of claim 10, wherein the dryelectrode film comprises about 1 wt. % to about 7 wt. % of the porouscarbon material.
 13. The dry electrode film of claim 10, wherein theporous carbon material comprises activated carbon.
 14. The dry electrodefilm of claim 1, wherein the dry electrode film further comprises aconductive additive.
 15. The dry electrode film of claim 14, wherein thedry electrode film comprises at most about 5 wt. % of the conductiveadditive.
 16. The dry electrode film of claim 14, wherein the conductiveadditive comprises a conductive carbon material.
 17. The dry electrodefilm of claim 16, wherein the conductive carbon material comprisescarbon black.
 18. An electrode comprising the dry electrode film ofclaim 1 in contact with a current collector.
 19. An energy storagedevice comprising the electrode of claim
 18. 20. The energy storagedevice of claim 19, configured to have a first cycle device efficiencyof at least about 90%.
 21. The energy storage device of any one of claim20, configured to have a first cycle device efficiency of about 90% toabout 94%.
 22. The energy storage device of claim 19, wherein the energystorage device is a battery.
 23. A method of fabricating the dryelectrode film of claim 1 for an energy storage device, comprising:mixing the dry active material with the dry binder to form a dryelectrode film mixture; and calendering the dry electrode film mixtureto form the dry electrode film.
 24. The method of claim 23, whereincalendering the dry electrode film mixture comprises at most threepasses through a calender.
 25. The method of claim 23, furthercomprising mixing the dry active material with a porous carbon materialto form a dry active material mixture, wherein mixing the dry activematerial with the dry binder comprises mixing the dry active materialmixture with the dry binder.
 26. The method of claim 25, wherein atleast one of the mixing of the dry active material and the porous carbonmaterial and the mixing of the dry active material mixture with a drybinder is performed by a non-destructive mixing process.
 27. The methodof claim 26, wherein the non-destructive mixing process is a resonantacoustic mixing process.
 28. The method of claim 26, wherein thenon-destructive mixing process is performed by a blade type mixer with atip speed of about 10 meters/min to about 40 meters/min.
 29. The methodof claim 25, wherein at least one of the mixing of the dry activematerial and the porous carbon material and the mixing of the dry activematerial mixture with a dry binder is performed by a high shear process.30. The method of claim 29, wherein the high shear process comprises ajet milling process.